ZL6105ALAF datasheet(25/35 Pages) INTERSIL

25 / 35 page

ZL6105

FN6906.5

December 19, 2013

2. Ratiometric. This mode configures the ZL6105 to ramp its

output voltage at a rate that is a percentage of the voltage

applied to the VTRK pin. The default setting is 50%, but an

external resistor string may be used to configure a different

tracking ratio.

Figure 15 illustrates the typical connection and the two tracking

modes.

The master ZL6105 device in a tracking group is defined as the

device that has the highest target output voltage within the

group. This master device will control the ramp rate of all

tracking devices and is not configured for tracking mode. A delay

of at least 10ms must be configured into the master device using

the SS pin, and the user may also configure a specific ramp rate

using the SS pin. Any device that is configured for tracking mode

will ignore its soft-start delay and ramp time settings (SS pin) and

its output will take on the turn-on/turn-off characteristics of the

reference voltage present at the VTRK pin. All of the ENABLE pins

in the tracking group must be connected together and driven by a

single logic source. Tracking is configured via the I2C/SMBus

interface by using the TRACK_CONFIG PMBus command. Please

refer to Application Note AN2033 for more information on

configuring tracking mode using PMBus.

When a current sharing rail is tracking, the on-delay time of the

voltage being tracked must not exceed the on-delay of the

tracking rail by 5ms.

Voltage Margining

The ZL6105 offers a simple means to vary its output higher or

lower than its nominal voltage setting in order to determine

whether the load device is capable of operating over its specified

supply voltage range. The MGN command is set by driving the

MGN pin or through the I2C/SMBus interface. The MGN pin is a

tri-level input that is continuously monitored and can be driven

directly by a processor I/O pin or other logic-level output.

The ZL6105’s output will be forced higher than its nominal set

point when the MGN command is set HIGH, and the output will

be forced lower than its nominal set point when the MGN

command is set LOW. Default margin limits of VNOM ±5% are

pre-loaded in the factory, but the margin limits can be modified

through the I2C/SMBus interface to as high as VNOM + 10% or as

low as 0V, where VNOM is the nominal output voltage set point

determined by the V0 and V1 pins. The ZL6105-01 allows 150%

margin limits.

The margin limits and the MGN command can both be set

individually through the I2C/SMBus interface. Additionally, the

transition rate between the nominal output voltage and either

margin limit can be configured through the I2C interface. Please

refer to Application Note AN2033 for detailed instructions on

modifying the margining configurations.

I2C/SMBus Communications

The ZL6105 provides an I2C/SMBus digital interface that enables

the user to configure all aspects of the device operation as well

as monitor the input and output parameters. The ZL6105 can be

used with any standard 2-wire I2C host device. In addition, the

device is compatible with SMBus version 2.0 and includes an

SALRT line to help mitigate bandwidth limitations related to

continuous fault monitoring. Pull-up resistors are required on the

I2C/SMBus as specified in the SMBus 2.0 specification. The

ZL6105 accepts most standard PMBus commands. When

controlling the device with PMBus commands, it is

recommended that the enable pin is tied to SGND.

I2C/SMBus Device Address Selection

When communicating with multiple SMBus devices using the

I2C/SMBus interface, each device must have its own unique

VOUT

Time

Coincident

Ratiometric

VTRK

VIN

VOUT

VTRK

VOUT

Time

VTRK

FIGURE 15. TRACKING MODES

TABLE 20. TRACKING RESISTOR SETTINGS

RSS

Ω)

TRACK

RATIO

(%)

UPPER TRACK

LIMIT

RAMP-UP/DOWN BEHAVIOR

90.9

100

Limited by target

Output does not decrease

before PG

100

Output always follows VTRK

110

Limited by VTRK

Output does not decrease

before PG

121

Output always follows VTRK

133

Limited by target

Output does not decrease

before PG

147

Output always follows VTRK

162

Limited by VTRK

Output does not decrease

before PG

178

Output always follows VTRK

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